Anthocyanins (also anthocyans; from Greek: (anthos) = flower + (kyanos) = blue) are water-soluble vacuolar pigments that may appear red, purple, or blue according to pH. They belong to a parent class of molecules called flavonoids synthesized via the phenylpropanoid pathway; they are odorless and nearly flavorless, contributing to taste as a moderately astringent sensation. Anthocyanins occur in all tissues of higher plants, including leaves, stems, roots, flowers, and fruits. Anthoxanthins are their clear, white to yellow counterparts occurring in plants. Anthocyanins are derivatives of anthocyanidins which include pendant sugars. Anthocyanins provide the purple color of the vertical stripes on stem of this JalapeÃ±o cultivar. Red color in Fuji applesIn flowers, bright reds and purples are adaptive for attracting pollinators. In fruits, the colorful skins also attract the attention of animals, which may eat the fruits and disperse the seeds. In photosynthetic tissues (such as leaves and sometimes stems), anthocyanins have been shown to act as a "sunscreen", protecting cells from high-light damage by absorbing blue-green and UV light, thereby protecting the tissues from photoinhibition, or high-light stress. This has been shown to occur in red juvenile leaves, autumn leaves, and broad-leaved evergreen leaves that turn red during the winter. It has also been proposed that red coloration of leaves may camouflage leaves from herbivores blind to red wavelengths, or signal unpalatability, since anthocyanin synthesis often coincides with synthesis of unpalatable phenolic compounds In addition to their role as light-attenuators, anthocyanins also act as powerful antioxidants. However, it is not clear as to whether anthocyanins can significantly contribute to scavenging of free-radicals produced through metabolic processes in leaves, since they are located in the vacuole and, thus, spatially separated from metabolic reactive oxygen species. Some studies have shown that hydrogen peroxide produced in other organelles can be neutralized by vacuolar anthocyanin. Occurrence Juvenile anthocyanin in new rose growth. The reddish hue disappears as the new leaves mature.Food source Anthocyanin content in mg per 100 g aÃ§aÃ 320 blackcurrant 190-270 chokeberry 1,480 eggplant 750 orange 200 Marion blackberry 317 black raspberry 589 raspberry 365 wild blueberry 558 cherry 350-400 redcurrant 80-420 red grape 888 red wine 24-35 purple corn 1,642 Anthocyanins are found in the cell vacuole, mostly in flowers and fruits but also in leaves, stems, and roots. In these parts, they are found predominantly in outer cell layers such as the epidermis and peripheral mesophyll cells. Most frequent in nature are the glycosides of cyanidin, delphinidin, malvidin, pelargonidin, peonidin, and petunidin. Roughly 2% of all hydrocarbons fixated in photosynthesis are converted into flavonoids and their derivatives such as the anthocyanins. There is no less than 109 tons of anthocyanins produced in nature per year. Not all land plants contain anthocyanin; in the Caryophyllales (including cactus, beets, and amaranth), they are replaced by betalains. However, anthocyanins and betalains have never been found in the same plant. Plants rich in anthocyanins are Vaccinium species, such as blueberry, cranberry and bilberry, Rubus berries including black raspberry, red raspberry and blackberry, blackcurrant, cherry, eggplant peel, black rice, Concord grape and muscadine grape, red cabbage, and violet petals. Anthocyanins are less abundant in banana, asparagus, pea, fennel, pear, and potato, and may be totally absent in certain cultivars of green gooseberries. The highest recorded amount appears to be specifically in the seed coat of black soybean (Glycine max L. Merr.) containing some 2,000 mg per 100 g and in skins and pulp of black chokeberry (Aronia melanocarpa L.) (table). However, the Amazonian palmberry, aÃ§aÃ, having about 320 mg per 100 g of which cyanidin-3-glucoside is the most prevalent individual anthocyanin (approximately 10 mg per 100 g), is also a high-content source for which only a small fraction of total anthocyanins has been determined to date. Due to critical differences in sample origin, preparation and extraction methods determining anthocyanin content, the values presented in the adjoining table are not directly comparable. Nature, primitive agriculture, and plant breeding have produced various uncommon crops containing anthocyanins, including blue- or red-flesh potatoes and purple or red broccoli, cabbage, cauliflower, carrots, and corn. Tomatoes have been bred conventionally for high anthocyanin content by crossing wild relatives with the common tomato to transfer a gene called the anthocyanin fruit tomato ("aft") gene into a larger and more palatable fruit. Tomatoes have also been genetically modified with transcription factors from snapdragons to produce high levels of anthocyanins in the fruits. Anthocyanins can also be found in naturally ripened olives, and are partly responsible for the red and purple colors of some olives. Autumn leaf color A selected purple-leaf cultivar of European BeechPlants with abnormally high anthocyanin quantities are popular as ornamental plants. Many science textbooks incompletely state that autumn coloration (including red) is the result of breakdown of green chlorophyll, which unmasks the already-present orange, yellow, and red pigments (carotenoids, xanthophylls, and anthocyanins, respectively). While this is indeed the case for the carotenoids and xanthophylls (orange and yellow pigments), anthocyanins are not synthesized until the plant has begun breaking down the chlorophyll, it is presumed for photoprotection during nitrogen translocation.